Medical Microbiology

268 4 BacteriaasHumanPathogens

Directidentificationinpatientmaterial.Molecularmethodsusedfordirect

detectionoftheM.tuberculosiscomplexin(uncultured)testmaterial.These

methodsinvolveamplificationofthesearchsequence.

Therapy.Thepreviousmethodoflong-termtherapyinsanatoriumshasbeen

replacedbyastandardizedchemotherapy(seeTable4. 4 forexamples),often

onanoutpatientbasis.

Epidemiologyandprevention.Tuberculosisisendemicworldwide.Thedis-

easehasbecomemuchlessfrequentindevelopedcountriesinrecentde-

cades,whereitsincidenceisnowaboutfiveto 15 newinfectionsper

100000 inhabitantsperyearandmortalityratesareusuallybelowone

per 100000 inhabitantsperyear.Seenfromaworldwideperspective,how-

ever,tuberculosisisstillamajormedicalproblem.Itisestimatedthatevery

yearapproximately 15 millionpersonscontracttuberculosisandthatthree

milliondieofthedisease.Themainsourceofinfectionisthehumancarrier.

Therearenohealthycarriers.Diseasedcattlearenotasignificantsourceof

infectioninthedevelopedworld.Transmissionofthediseaseisgenerally

direct,inmostcasesbydropletinfection.Indirecttransmissionviadustor

milk(uddertuberculosisincattle)istheexceptionratherthantherule.

Theincubationperiodisfourto 12 weeks.

&Exposureprophylaxis.Patientswithopentuberculosismustbeisolated

duringthesecretoryphase.SecretionscontainingTBmustbedisinfected.Tu-

berculouscattlemustbeeliminated.

&Dispositionprophylaxis.Anactivevaccineisavailablethatreducesthe

riskofcontractingthediseasebyaboutone-half.Itcontainsthelivevaccine

BCG(lyophilizedbovineTBoftheCalmette-Gue ́rintype).Vaccinationof

tuberculin-negativepersons inducesallergyand(incomplete)immunity

thatpersistforaboutfiveto 10 years.Incountrieswithlowlevelsoftuber-

culosisprevalence,theadvisorycommitteesonimmunizationpracticesno

longerrecommendvaccinationwithBCG, eitherintuberculin-negative

childrenathighriskorinadultswhohavebeenexposedtoTB.Preventive

chemotherapyofclinicallyinapparentinfections(latenttuberculosisbacteria

infection,LTBI)withINH(30 0 mg/d)overaperiodofsixmonthshasproved

effectiveinhigh-riskpersons,e.g.,contactpersonswhothereforebecame

tuberculin-positive,intuberculin-positivepersonswithincreasedsuscept-

ibility(immunosuppressivetherapy,therapywithcorticosteroids,diabetes,

alcoholism)andinpersonswithradiologicallyconfirmedresidualtuber-

culosis.Compliancewiththetherapeuticregimenisaprobleminpreventive

chemotherapy.

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Kayser, Medical Microbiology © 2005 Thieme